A drag chain is an essential part of the machinery used in a wide range of industries. Conveyor belts, robots, and CNC machines are all places where a drag chain is needed to keep moving parts running smoothly. However, there is no one-size-fits-all solution to industry needs, so understanding how they are used and their function is critical.
Whether in a CNC machine or automation equipment, the cables in a drag chain are subjected to near-constant pulling, pushing, and twisting. They can also be exposed to harsh chemicals that cause serious corrosion or endure extreme weather conditions that may damage cables keeping the machine running. The drag chain houses these cables and keeps them out of harm’s way, but the cable itself must also be durable and well-suited for the chain in which it is housed.
There are many factors to consider when choosing a cable and a drag chain to house it. It can be challenging for someone to choose a good cable drag chain system, especially if they do not have much experience. The information below will help inexperienced users make the best choice of drag chain and cable for their specific use.
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What are Cable Drag Chains?
Drag chains are used in a vast number of industries and applications, including machine tools, automation technology, industrial robots, conveyors, cranes, and vehicle transporters. Drag chains essentially protect and support moving cables as the machinery they operate performs its tasks. It shields them from snags, tears, slips, tangles, corrosive chemicals, or other harsh conditions.
Drag chains are made of a series of metal and plastic parts linked together to allow the cables to move and twist according to the function of the machine they power. Drag chains are flexible but durable, taking on the brunt of the friction and stress that would otherwise be put on sensitive cables.
How to Choose the Best Cable Drag Chain
Cable drag chains are complex, offering both incredible flexibility and strength. Great care is needed when selecting the type of chain for a specific application, as conveyor systems will undergo different types of stress than robotic systems. It is equally important to plan for the layout of the cables inside the chain, as it is not a universal system.
Chain manufacturers should have detailed information on how to choose a cable drag chain for a variety of applications and instructions on the proper setup for maximum longevity of the entire system. Those guidelines are great places to start, but further customizations are often needed for smaller applications, such as in CNC machines. There are several things to consider when choosing the best cable drag chain, which is explained in greater detail below.
Cable Clearance in Chain
When selecting both cable and drag chain, cable clearance is a critical factor to consider. When taking measurements, it is best to add an extra ten percent to the diameter of a cable, which helps accurately identify the ideal size wire cavity inside of the drag chain. The minimum clearance for a cable should be greater than 1mm around the outside diameter of the wire.
For pneumatic lines, measurements should include an extra 15 percent added onto the outside diameter. Minimum clearance for these should be greater than 2mm. Hydraulic hoses should have an extra 20 percent added and the minimum clearance must be greater than 3mm.
Chain Fill
Cables within the chain should allow for space within each cavity according to the manufacturer’s recommended safety factor. The manufacturer will make this information available either online or through printed materials that come with the product. Cables can take up more space within the chain, but it could greatly reduce the lifespan of the entire system.
Additionally, it is important to consider weight distribution inside the chain. For example, larger cables should be situated on the outside of the drag chain, while smaller cables sit on the inside. If the larger cables are on one side with the smaller cables on the other, the weight could be thrown off and the chain will not run smoothly.
Bending Radius
Bending radius is a critical factor in choosing a cable drag chain. Manufacturers give cable chains a minimum bending radius, which is different depending on their ideal function. For example, the bending radius of a drag chain used inside of a conveyor belt will be fixed in one direction, whereas automation equipment will require more flexibility. Cable chains should always have a bending radius that is equal to or greater than the bending radius of the largest cable. The larger the bending radius that a cable chain has, the longer the cables it houses will last.
Cable Stress Types
The type of stress a cable will endure is a critical consideration when choosing a cable drag chain. Familiarity with these types of stress help to determine which drag chain is required for a system.
The first type of stress is called bending flex. Bending flex involves cables that are moving back and forth from a stationary point, similar to a tick-tock movement.
The second type of stress is called torsional flex. In these cases, a cable is twisted either counterclockwise or clockwise from its centerline in varying angles and rotations. This flex stress is often seen in robotics that requires constant flexing and twisting over a long period.
The last type of stress is called continuous flex. This stress involves the cable moving back and forth in a linear fashion, resulting in equal flex throughout the cable. Typically, this cable is only suitable for a carrier system that has a bend radius of ten times the cable’s the outside diameter or less.
Construction Types
There are three types of cable construction to note when choosing drag chain cable. Each cable construction has a type of cable stress for which it is designed. Be sure to note which cable is used before selecting a drag chain.
Unilay cable, or bunch cable, involves any number of wires twisted together like a rope. The wires are not arranged in any specific layer and are typically the most flexible. Concentric unilay cables have wires that are twisted in one direction and arranged in specific layers that all twist in the same fashion. Concentric unilay cables are not as flexible as regular unilay cables, but they are stronger.
Concentric contra-helical cables have wires that twist similar to the way unilay cables do but with well-defined layers of wire twisted in the opposite direction of the layers before or after it. These cables are the least flexible but are much stronger than unilay cables or concentric unilay cables.
Cable Drag Chain Use is Essential
Cable drag chain setups are complex, but they are essential for maintaining the functionality of the systems they operate and protecting their longevity. Drag chains are part of an underappreciated system at the heart of every major industry that contributes to the production of goods and industrial services throughout the world.
